It is common in printers to have means to change the size of the paper gap between cooperating elements of the print mechanism, such cooperating print elements being either print hammers and a type carrier, such as an engraved band or drum, of high speed impact line printers or the print head, wheel or other impression forming elements and the platen of serial type printers. The purposes of changing the gap size is setting the gap to accommodate different forms thickness and for backing the platen away such that there is clearance for loading forms, ribbons and print bands. Typically, there are two separate mechanisms to accomplish these tasks. The platen gap open mechanism holds the band drive unit against a stop when in the printing mode while the forms thickness mechanism controls the gap distance, which is set by an operator. When the platen gap open mechanism is actuated, the band drive unit is disengaged from it's stop and the entire band drive unit moves away from the printer hammers. The use of two such mechanisms can be expensive. An early example of this is shown in U.S. Pat. No. 3,155,032. Later examples of such gap changing mechanisms are found in U.S. Pat. Nos. 4,248,146; 4,773,772 and 4,932,797.
A gap adjusting mechanism having a single camming means and a single operator means therefor which is capable of achieving both forms thickness adjustment and gap opening for installation of forms is described in copending application Ser. No. 07/66,265, filed on 03/01/91 now U.S. Pat. No. 5,104,244. In that application, the camming means comprises cam elements which have a cam surface profile which produces either thickness adjustment or opening of the gap. In that mechanism, the thickness setting is lost when the operator is used to open the gap for installation of the forms. This invention is designed to enable gap opening with a return to the original thickness setting of the cams.